Abstract: This biologically compatible surgical prosthetic implant has a multi-layer coating formed from metallic particles having sizes which increase in the direction from the metallic body of the implant toward the surface of the coating which is to interface with bone. The gradation is achieved by first depositing a layer of small particles, for example microspheres, of metallic coating material on the surface of the implant, then depositing progressively larger particles in subsequent layers. The particles may be deposited by any one of a number of well-known processes including but not limited to a flame-plasma process, in which several parameters are controlled as functions of the size of the particles.The resultant coating has minimum density and maximum porosity at its outer surface to encourage ingrowth of bone.